Surgical probe for laparoscopy or intracavitary tumor localization

ABSTRACT

The surgical probe according to the invention includes a collimator, made of lead or a high Z, atomic number metal; a scintillating crystal sensitive to gamma ray having an energy in the range from 30 KeV and 1 MeV; a light guide system; a photomultiplier; and electronics capable of integrating and converting analog signals to digital signals. The probe can be used in either intracavitary mode, or in laparoscopic mode, by putting the probe in a specific trocar. The apparatus may automatically subtract the background; and may provide visualization on a monitor. The probe can also include a flexible tip, in order to enlarge the field of view which the probe can be used to examine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to with a surgical probe for laparoscopyand intracavitary tumour localization. A surgeon needs to localize atumour in order to remove it and thus he usually makes use of thetraditional diagnostic means to search for the tumour, such as: CAT,NMR, Scintigraphy. However during the operation, the surgeon can stillneed to better define the area to be cut and removed. Thus he can use aso-called "SURGICAL-PROBE": after injecting the patient with aradioisotope-doped drug capable of being absorbed by the tumour cells,the surgeon can detect the gamma radiations emitted by the radioisotopevia a probe practically acting as a Geiger-Muller detector.

The probe sensitivity to gamma radiations is such that it gives analogicsignals, whose number is proportional to the detected radioisotopeconcentration. The detected signals are then reversed into digitalsignals thus giving a luminous and/or noisy scale proportional to thedetected radioisotope concentration.

By tracing the most active area, the tumour site can be localised.

2. Description of the Related Art

As an example the "MARTIN PROBE", presently on the market, is acylindrical proportional tube, 30 mm in diameter, containing anionisable gas and two electrodes to which a high voltage is applied: thegamma rays are detected by gas ionising and electrical signal generatingmeans.

The availability of a small dimension probe with a good efficiency forlow energy rays would be desirable.

The Martin Probe, however, has an excessive hindrance and a weak lowenergy-rays efficiency thus resulting in:

1) a very rough spatial resolution, such as 4 cm, which gives a badtumour localisation

2) a bad tumour-to-background ratio resolution which makes the probe ofscarce utility.

It is then clear that the poor obtainable advantages are limiting theuse of the surgical probe.

Several probes are known on the market, all of them used in inintracavitary mode only, which is made of about 20 mm diametercylindrical tube having inside a scintillating crystal positioned on thetip of the tube, coupled with a photomultiplier.

When the gamma radiations emitted by the radio pharmaceutical,previously injected into the patient, hit the scintillating crystal, aspecific light is emitted and collected by the photomultiplier which, inturn, converts the optical into an electrical signal, which can then beused to vary a visible or voiced scale whose value is proportional tothe radiation intensity. Furthermore, being the probe active area of afew square centimeters with the possibility of collimation, the spacialresolution results to be limited to a few centimeters.

The use of the described probe is only limited to the intracavitary modeor, in other words, when necessarily the surgeon opens the patient.

It is desirable however to use a probe via laparoscopy to detect withhigh precision the sites where radioactive tracers cumulate and indicatethe presence of a tumour to be surgically removed, thus guiding thesurgeon toward the exact tumour position with the possibility todiscriminate tumoural from healthy tissue with a few millimeterprecision.

Before the surgical operation it would be necessary to precisely locatethe point of radioactive tracer maximum concentration together with thesurrounding area affected by the surgical removable tumour.

U.S. Pat. No. 5,429,133 discloses a laparoscopic instrument having ahand-grippable base to which an elongate accessing tube is connectedwhich extends to a tip. Extending inwardly from the tip is a detectionsupport region within which a radiation transmissive window is formed.Immediately spaced from and behind the window a detecting crystal suchas cadmium telluride is retained to detect the radiations emitted from a¹²⁵ I source and retained in a mount structure designed to minimizenoise generation due to microphonic (piezoelectric) phenomena.

PCT Application WO 94/03108, on which the preamble of present claim 1 isbased discloses a laparoscopic surgical probe for localizing tumours andcreating images of tumour affected radiation emitting organs comprisinga first section based upon scintillator means for receiving radiationrays emitted from said radiation emitting organs and converting theradiation rays into light signals, light transmission means to transmitthe light signals generated by said first section to a second sectionincluding a position sensitive light signal detector and electronicmeans for receiving said light signals and producing images of saidradiation emitting organs.

U.S. Pat. Nos. 5,014,708 and 5,088,492 disclose multi-function deviceswherein use is made of collimators in surgical probes.

BRIEF SUMMARY OF THE INVENTION

The present invention solves the above described problems. To thispurpose the invention deals with a gamma-ray sensitive surgical probewhich can be used both in laparoscopic or intracavitary mode to detecttissue areas affected by small size tumours.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed features and advantages of the invention will further resultfrom the following description with reference to the attached drawings,given as a non-limiting example and where:

FIG. 1 is an expanded view of the invention device where the composingparts are indicated;

FIG. 2 shows the collimator and the shield details;

FIG. 3 shows the scintillating crystal;

FIG. 4 shows the light guide scheme;

FIG. 5 shows the photomultiplier and a top view;

FIG. 6 shows the electron multiplication mechanism taking place insidethe photomultiplier (metal channel dynodes);

FIG. 7 shows the hardware electronics block lay-out;

FIGS. 8a and 8b show the hardware electronic block lay-out variationrelating to an imaging probe;

FIG. 9 shows a flexible probe variation.

With reference to the figs. the new probe and its components aredescribed:

--the collimator 1 made of lead or a high Z metal (such as W, Au, etc),which allows only the gamma-rays in a certain solid angle to passthrough the holes; the collimator has a 10 mm diameter;

--a scintillating crystal 2 made of YAP:Ce (Ittrium alluminate Ceriumdoped with perovskite structure) sensitive to gamma rays with energyranging from 30 KeV to 1 MeV, emitting light with 380 nm peakwavelength; the crystal has a 6 mm diameter;

--a tungsten shield 3 to protect the scintillating crystal from gammarays coming from side direction;

--a light-guide system 4, optically coupled to the scintillating crystalon one side and to the photomultiplier on the other side, having 8 mmdiameter and about 200 mm long;

--a jacket 5 made of inert and sterilizable material for the part to beintroduced into the patient, having 11 mm diameter and about 250 mmlong;

--a container 6 for incapsulating the photomultiplier;

--a photomultiplier 7 collecting the optical signal guided by the lightguide and modifying it into an electrical signal. The photomultiplierused is a compact type made of 8 thin metallic channels dynodesincapsulated into a 15 mm diameter and 10 mm thick cylinder as shown inFIG. 5, and position sensitive via a charge collecting multi-anodesystem shown in FIG. 6;

--an electronic hardware 10 to integrate and convert the analog signalsinto digital signals, giving in real time a measure proportional to thedetected signals.

The hardware shown in FIG. 7 includes:

--a preamplifier 9 and resistive voltage divider of the photomultiplier8, integrated and assembled inside the probe; the probe detected signalenters into a varying gain amplifier 9 connected to three parallelfunctional blocks;

--an impulse detector 11 giving a signal proportional to the probedetected gamma radiation;

--an impulse synchroniser 12 generating a synchronism signal when animpulse maximum value is reached;

--a sampler 13 (sample and hold), governed by a first monostable device14 which exactly synchronise the sampler with the maximum impulse.

The sampler is linked to a window selecting circuit 15, which allows toselect two or more energy windows, called A, B, etc, adapting andoptimising the probe answer to the several radioisotopes used.

The said window selecting system is linked to a second monostable device16, generating impulses reaching both a sound emitter device 17 and acouple of luminous led bar visualising blocks 18, crossing through afilters and amplifiers chain 20.

The luminous visualising blocks allow to see both the impulse frequency21 and the actual probe position frequency in respect to the frequencymaximum 19.

FIG. 9 shows a variation of the invention where it is possible toslightly bend the probe's tip via an externally guided knob system sothat also hardly accessible sites can be screened and detected and alarger volume can be explored.

The jacket 5, as already said, is entirely made of inert andsterilisable material, while the part of the probe remaining outside thepatient body, is made of a 30 mm diameter and about 100 mm longcylinder.

Via the introduction of the probe through a "trocar" (laparoscopicprobe), or via the intracavitary mode, into the body of a patient whichhas been previously injected with a radioisotope doped drugpreferentially cumulating onto the tumour cells and emitting 30 KeV to 1MeV gamma rays, the surgeon can trace the tumour by finding the maximumgamma emitting site with a precision up to about 5 mm.

This gives the surgeon the possibility to operate with high precisiononly in the tumour affected area, thus reducing the surgery induceddamages and the patient risk.

Furthermore the high sensitivity of the probe allows the use of energygraded isotopes and gives the possibility to dope specific anti-bodywith various radioisotopes for specific tumours.

In possible variations of the invention, the laparoscopic surgical probecan use a matrix of scintillating crystals having a section of about 1×1mm and within the range 0.5×0.5 mm to 2×2 mm, where the crystals areoptically separated one from the other, and the crystal to crystalseparating set is about 0.1 mm thick and within 3 microns to 0.5 mm.

Furthermore scintillating crystals such as CsI(Tl), NaI, (Tl), BGO, LSOetc., can be used, and the light guide can be made with plastic materialhaving refractive index within 1.41 to 1.62 such as PMMA, PS, PC etc.,optically coupled both with the scintillating crystal and to thephotomultiplier.

In a possible variation the light-guide system is made of onelight-guide or optical fibre, to collect the main signal, surrounded byother light-guides or optical fibres, made of the same material buthaving smaller section, to collect the background signal. Thelight-guides or optical fibres can have a cylindrical or differentsection and they are each-other optically separated.

In another possible variation, the light-guides system is replaced by abundle of optical fibres bundle, each-other optically separated, havingon one side an overall section equal to the total section of thescintillating crystal and being optically coupled to the latter, withoutleaving any dead space; furthermore having an overall section equal tothe active window of a photomultiplier on the other side. These singlefibres have a round, square, exagonal or variable section with 0.3 to 2mm diameter or side-side distance.

Moreover, said light-guides can be replaced by light-guides or opticalfibres made of an inorganic material such as silica, quartz, etc..

In a variation of the invention the optical fibre guided signal iscollected by a photomultiplier with 8 mm diameter active window andsensible to the single photon, or via a position sensitivephotomultiplier which has a metal channel dynode system to improve thespacial resolution up to about 2 mm.

In another possible variation of the invention, the photomultiplier isreplaced by a solid state detector such as a silicium, gallium arsenide,or avalanche photodiode having pixel of about 0.5×0.5 mm or within0.2×0.2 mm to 2×2 mm, capable to read light photons, and determining theposition and the energy absorbed by the scintillating crystal during thegamma-ray interaction.

Via the electronic circuit shown in FIG. 7, the photomultiplier analogicsignals can be converted into visible or sound digital signalsproportional to the detected gamma-rays intensity thus localising themaximum concentration of radio-tracer (tumour).

The invention takes also in consideration the integration of all thesignals and their convertion via soft-ware into real-time imaging, togive the gamma-rays distribution with a spacial resolution of about 2mm.

In another variation of the invention, the laparoscopic surgical probecan be introduced through a 12 mm diameter trocar into the body of apatient, the probe being made of an inert and sterilizable material suchas teflon, stainless steel or similar, and the portion introducedthrough the trocar can be flexible so that the tip can be bent via anexternal guide knob system and which allows to scan a bigger portion ofarea.

Whereas the overall length of the probe of the invention is about 35cm., the portion introduced through the trocar is about 25 cm long orwithin 10 cm to 30 cm, and has about 11 mm diameter or within 10 mm to18 mm, and the portion remaining out of the trocar is about 100 mm longand about 30 mm in diameter.

According to the invention, the probe is connected to a systemvisualising both the intensity and maximum intensity position of thegamma-rays, via a colour scale and a voiced system both proportional tothe gamma radiation intensity.

Furthermore in another variation of the invention an innovation in thefield of the data acquisition, transfer and management system for thelaparoscopic surgical probe is presented.

A microprocessor chip, with a particular software program, is theintelligent interface between the probe electronics and a personalcomputer. A graphic program besides handles the data presentation.

A charged particle or a gamma photon passing through the scintillatingcrystal represents an event memorised by the acquisition system togetherwith the measured energy, the time and, eventually the probe position.

The microprocessor transfers at the same time the event data to thecomputer.

A graphic program handles the event data visualization on the personalcomputer monitor.

Tumour sites localization is based on the tumour to background countingratio and so the graphic program allows the visualization of the countsnumber as a function of time.

Once chosen a time window period, in the range between 10s and 90s, theprobe use protocol suggests that the surgeon shall move the probe at aconstant speed in such a way as to carry out a scanning of the area ofinterest: each zone, placed in front of the probe tip, has a radioactiveemission which is correlated to the measured counts number and thecounting rate visualization represents an imaging of the investigatedarea radioactivity.

In case a maximum of activity has been found in the first scanning, thenthe maximum emission point can be found out again by moving the probeback to the scanned way as long as the actual counting rate equals theprevious peak value which remains on the PC screen for a maximum periodof 90s.

The tumour sites localization is also based on the energy selection.

The graphics program carries out the visualization of the incidentgamma-ray energy spectrum, thus allowing, on one hand the detectorcalibration according to the used radioactive tracer, and, on the otherhand, the energy selection window: the acquisition program selectsevents which, coming from the zone in front of the probe tip withoutbeing scattered and without loosing energy, have an energy which ischaracteristics of the photoelectric peak, events scattered by Comptoneffects, are rejected, on the basis of an energy lower than thephotoelectric peak value, because they are not coming directly from thezone investigated by the probe.

The imaging capability is based on the possibility of coupling ameasured counting rate and the investigated area space position of theprobe.

Keeping this in mind another aspect of the invention is that a positionrecognition device and an engine, moving the probe along a X-Y plane, iscoupled to the probe--electronics--personal computer system.

An automatic scanning program carries out the counting rate measurementfor different probe positions along a plane, in order to obtain theimage of the examined zone radioactive emission.

Finally the radiation intensity visualising system can be replaced by areal time imaging system which allows to see the whole probe exploredarea by showing a light-colour intensity proportional to the gamma-raysintensity, with a spatial resolution up to about 2 mm.

Obviously, the construction details and the embodiments can widely varyin respect to what described and shown as a simple example, withoutdeparting from the scope of the present invention.

We claim:
 1. A laparoscopic surgical probe for localizing tumors andcreating images of tumor-affected radiation emitting organs, saidlaparoscopic surgical probe comprising:first components, includingacollimator member and a scintillator means for receiving radiation raysemitted from the radiation emitting organs and converting the radiationrays into light signals; a light transmission means to transmit thelight signals generated by said first components to second components,includinga position sensitive light signal detector and an electronicmeans for receiving said light signals and producing images of saidradiation emitting organs, wherein(a) said first components, said lighttransmission means and said second components form a unitary body probe;(b) a converting means is provided, which are adapted to receive andconvert radiation emitted from the radiation emitting organs in theenergy range of 30 KeV to 1 MeV; and (c) said collimator member has asection in the range between 6 mm and 15 mm, with a hole having 3 mm to10 mm diameter, with a wall thickness in the range between 0.1 mm and 4mm and with a length in the range between 5 mm and 50 mm.
 2. Alaparoscopic surgical probe according to claim 1, wherein said firstcomponents further comprisea collimator member comprised of lead oranother high Z metal which allows gamma ray passage through its holeonly, and within a precise solid angle; the collimator having anexternal diameter between 10 mm and 15 mm; a scintillating crystal,sensitive to gamma rays having energy between 6 KeV and 1.3 MeV,emitting a blue or green light; the crystal having an external diameterin the range between 6 mm and 10 mm; a tungsten shield, to shield thescintillating crystal from gamma rays coming from lateral directions;and wherein said transmission means include:a light guide system,optically coupled to the scintillating crystal on one side and to thephotomultiplier on the other side, having a 8 mm cross section and being200 mm in length; a jacket made of an inert and sterilizable material,which has a cylindrical shape with a diameter in the range of 10 mm to15 mm and 250 mm in length; and wherein said second components include:acontainer to house the photomultiplier; a photomultiplier which turnsthe scintillation light pulse into an amplified electrical signal andwhich is a very compact one in which dynodes are stored in a cylindricalhaving a diameter in the range of 10 mm to 15 mm and a length in therange of 10 mm to 45 mm; an electronic circuit which converts the analogsignals to digital ones, giving in real time a measurement of theintegrated charge, which is proportional to the energy of the incidentparticle, and a measurement of the number of the gamma rays, interactingaccording to photoelectric effect in the scintillating crystal, as afunction of time or probe position.
 3. A laparoscopic surgical probeaccording to claim 2, wherein said scintillator means comprise a matrixof scintillating crystals, each crystal having a cross section in therange between (0.5×0.5) square mm and (2×2) square mm and beingoptically separated from the other ones, and the separation between thecrystals having a thickness in the range from 3 microns to 0.5 mm.
 4. Alaparoscopic surgical probe according to claim 3, wherein saidscintillating crystal is selected from the group consisting of CsI (Tl),NaI (Tl), BGO, and LSO crystals.
 5. A laparoscopic surgical probeaccording to claim 4, wherein said light guide is made of a materialhaving a refractive index between 1.41 and 1.62.
 6. A laparoscopicsurgical probe according to claim 1, wherein the scintillating crystalis directly optically coupled to the photomultiplier.
 7. A laparoscopicsurgical probe according to claim 1, wherein the scintillating sensitivedetector and the light guide are comprised of a central part to collectthe signal coming from the main source and of a peripherical part tocollect the signal coming from the background, the central part beingmade of a crystal coupled to a light guide or an optical fiber ofsimilar cross section, while the surrounding part is comprised of a fewcrystals coupled to light guides or optical fibers having a smallercross section than the central part ones, and where both the individualscintillating crystals and the light guides or optical fibers areoptically separated from each other.
 8. A laparoscopic surgical probeaccording to claim 1, wherein the light guide is comprised of an opticalfiber bundle, having a cross section which, on one side, is equal to thetotal surface of the scintillating crystal, and, on the other side, issimilar to the active area of the photomultiplier without formation ofdead zones, and said fibers have a square or circular or hexagonal crosssection and a diameter or side-side dimension ranging from 0.3 mm to 2mm.
 9. A laparoscopic surgical probe according to claim 1, wherein theplastic light guides or optical fibers are substituted by light guidesor optical fibers made of an inorganic material such as silica, quartz,etc.
 10. A laparoscopic surgical probe according to claim 1, wherein theoptical fiber guided signal is collected by a photomultiplier with an 8mm diameter active window and is responsive to the single photonemission.
 11. A laparoscopic surgical probe according to claim 1, saidposition sensitive photomultiplier has a metal channel dynode system toimprove the spacial resolution up to 2 mm.
 12. A laparoscopic surgicalprobe according to claim 1, wherein the photomultiplier is replaced by asolid state detector, with pixels of from 0.2×0.2 mm to 1×1 mm, whichreads light photons, and which indicates the position and the energyabsorbed by the scintillating crystal during interaction with the gammaray.
 13. A laparoscopic surgical probe according to claim 12, wherein anelectronic circuit converts the photomultiplier analog signals intovisible or voiced digital signals.
 14. A laparoscopic surgical probeaccording to claim 13, wherein the visible and voiced digital signalsare proportional to the detected gamma ray intensity, thus indicatingthe position of the highest radiotracer concentration.
 15. Alaparoscopic surgical probe according to claim 14, wherein the signalsare integrated and, via software, transformed into a real time imaging,to give images showing gamma ray emission distributions with a spatialresolution up to 2 mm.
 16. A laparoscopic surgical probe according toclaim 1, wherein the probe is jacketed with inert and sterilizablematerial and is introduced into a trocar having a 12 mm minimum internaldiameter.
 17. A laparoscopic surgical probe according to claim 16,wherein the probe introduced into the trocar is flexible so that the tipportion can be bent via an externally guided knob system to scan alarger area.
 18. A laparoscopic surgical probe according to claim 17,wherein the overall length is 35 cm and the portion introduced into thetrocar is from 10 cm to 30 cm long, and from 6 mm to 22 mm in diameter,and the external portion is 100 mm long and 30 mm in diameter.
 19. Alaparoscopic surgical probe according to claim 1, wherein, via dedicatedsoftware, a graphic program handles the event data visualization on apersonal computer monitor and the tumor site localization is based onthe tumor to background counting ratio, thus allowing the graphicalvisualization of the count numbers as a function of time.
 20. Alaparoscopic surgical probe according to claim 19, wherein the dedicatedsoftware graphic program carries out the visualization of the incidentgamma-ray energy spectrum, thus allowing, on one end, the detectorcalibration according to the used radioactive tracer, and, on the otherend, the energy selection window, and where acquisition program selectsevents which enter directly the detector without scattering, thus havingan energy characteristic of the photoelectric peak, while rejectingevents scattered by Compton effects and having an energy lower than thephotoelectric peak.
 21. A laparoscopic surgical probe according to claim20, wherein the gamma ray intensity and the maximum intensity positionare visualized via a luminous color scale and a voiced system both ofwhich are proportional to the gamma ray intensity.
 22. A laparoscopicsurgical probe to according to claim 21, wherein the intensityvisualization system is replaced by a real time imaging to see all theinvestigated area by showing the light-color intensity proportionally tothe gamma ray intensity with a spacial resolution up to 2 mm.